1. Field of the Invention
The present invention relates to the general art of optics, and to the particular field of eye examinations.
2. Description of the Related Art
The size of an individual's pupils is important in neurological and cranial nerve evaluation as well as a fast indication of a brain injury as well as an indication of diseases, such as Alzeheimer's disease or the like and for detecting fatigue, or for detecting alcohol or chemical/substance abuse, or the like and for use in glaucoma screening capability, corneal topography measurement capability, intracranial pressure detection capability, and ocular aberration measurement capability. Furthermore, it is known that the response of an individual's pupil to external light stimulation yields useful information as to the subject's well being. Analysis of an individual's pupil is an effective and non-invasive means of characterizing a subject's brain, nervous and cranial conditions.
Thus, devices for analyzing a subject's pupil may be useful in the medical, transportation, military and law enforcement fields, in industry, and in other areas in which it is desirable to detect such conditions.
The inventor is aware of some devices for performing neurological assessment which include holding a millimeter gauge over the eyes or by subjectively giving a number to the eye diameter. The size of eye pupil is normally equal at rest among a great percentage of individuals. Some individuals are born with unequal pupil size without any underlying pathology. However, the methods known to the inventor are not as accurate as possible.
For some applications, it is desired to monitor the time-response of the individual's pupil as the eye is subjected to various lighting conditions. As an example, such a device would measure the pupil response of a dark-adjusted eye that is subject to a stimulating light pulse (i.e. photostimulus). For such an example, the pupil, initially large due to the dark-adjusted state, will typically decrease in size in response to an external light stimulation flash, and then increase in size upon returning to a dark-adjusted condition.
For example pupilometers are often used in an analysis of a subject. Briefly, conventional pupilometers typically include optical-electronic apparatus for generating a pupillary response-inducing light stimulus, and for measuring the diameter of the stimulated pupil over a period of time to establish the response (including parameters such as pupil constriction velocity, initial, minimum and final pupil diameter, time to minimum, and reflex amplitude) of a user/subject's pupils to the light stimulus. To this end, conventional pupilometers typically include one or more visible light emitting diodes to produce the response-inducing light stimulus (i.e., diodes to generate a visible flash of light directed along an optical path and at the subject's eye to cause contraction of the subject's pupil), and infrared diodes or other IR source and associated optics and electronics adapted to direct the IR source to and from the subject's eye for measuring the dynamic pupillary response to the light stimulus. Some methods and apparatus for measuring pupillary response generally utilize either a pupil imaging technique or a light scattering detection technique.
As can be understood from the foregoing, any analysis of a subject's pupil requires an accurate reading of pupil size.
Some imaging methods and apparatus rely on imaging the eye (or a portion thereof) on a detection device such as charged-coupled device (CCD), or other optical detector array. In these instances, the image of the eye, or a portion thereof, is typically detected on a two-dimensional detection device or a scanning one-dimensional device. The output of the imaging device is processed to determine the size of the pupil or other desired pupillary response data.
Often, especially in emergency situations, such pupil size measurement must be conducted in the field and under adverse conditions. While the inventor is aware of several devices that can analyze a pupil, such as used in pupilometry, the inventor is not aware of any device that can provide rapid and accurate pupil measurements and yet which is also simple and easy to operate.
Therefore, there is a need for an accurate and simple means for reading pupil size.
A further difficulty with many of the techniques known to the inventor is that the technique measures only relative pupil response; the inventor is not aware of methods and apparatus for absolute measurement of the pupil diameter during pupillary response measuring techniques.
Therefore, there is a need for a means for providing an absolute measurement of the pupil diameter.
In addition to the above-mentioned deficiencies in the prior art, there is a lack of practical pupil analysis devices that are cost-effective and relatively simple and compact, and thus suitable for use in portable, hand-held situations.
Therefore, there is a need for a practical pupil analysis device that is cost-effective and relatively simple and compact, and is thus suitable for use in portable, hand-held situations.